The main theme of this proposal is to examine the cellular and molecular mechanisms that contribute to plasticity of behavior in mammalian and invertebrate (the marine mollusc Aplysia californica) nervous systems. Experimental analyses of behavioral plasticity will be approached by using a combination of electrophysiological, biochemical, morphological, and molecular genetic techniques to examine three types of factors: learning, motivation, and development. Individual research projects are designed to promote interdisciplinary collaboration between 10 individual laboratories in the Center for Neurobiology and Behavior. To simplify the cell and molecular analysis of behavior, three principal experimental systems will be employed: 1. semi-intact systems in which neuronal activity can be recorded while the organism exhibits behavioral responses; 2. reduced systems of isolated ganglia of Aplysia; and 3. cell culture systems in which experimental control can be greatly increased. We will use semi- intact preparations of vertebrates (the cat) as well as invertebrates (Aplysia) to investigate three types of problems: a) plasticity of motor behavior, using a restrained cat engaged in a tracking task; b) simplified forms of learning, using Aplysia; and c) alterations of motivational state, using a preparation of Aplysia that exhibits various types of plasticity of feeding behavior. We will use reduced systems to observe analogs of learning and motivational state. We will use cell culture to a) study synaptic transmission of vertebrate sensory neurons and axonal growth of vertebrate and invertebrate neurons; and b) to reconstitute a system that exhibits analogs of learning that can be studied in parallel with the more complex systems referred to above. A comparison of vertebrate and invertebrate neural systems should provide insights into general mechanisms that contribute to plasticity of behavior.